When a large number of PCI (Peripheral Components Interconnect) cards are to be loaded in a large-scaled system, a lack of system resources is worried. Especially, a Legacy-IO (Input/Output) space is limited to 64 KB (Kilo Bytes). Because the IO space of 4 KB per bridge device (slot) is basically assigned, 16 slots at a maximum can be only assigned to the IO space.
There are two measures against this situation. A first measure is to assign the IO space in units of 1-KB granularities. Here, the granularity is a “process segmentation unit” in segmenting a process into sub processes and assigning the sub processes to a plurality of processors for processing a large amount of numerical data in a large-scaled multiprocessor system. The 1-KB granularity shows that a granularity unit is 1 KB. More specifically, a chipset has a function to permit IO space assignment in units of 1-KB granularities, and this function is utilized. Since this method goes beyond the PCI standard specification, there is no problem when a bridge device is not made conscious directly as in Pre-Boot environment but it is necessary to hide the bridge device for an OS (Operating System). However, in a device of a PCI-Express generation in place of a PCI card, a root port of the PCI-Express which is equivalent to a bridge device is directly controlled by the OS to allow a PCI-Express function to be effectively used. For this reason, it means inhibition of the PCI-Express function to hide the bridge device to the OS supporting the PCI-Express.
A second measure is a method of using an “extended IO space” in which an IO space of 64 KB or more can be assigned. A method of accessing to a function of the extended IO space is defined in ACPI standard specification (Advanced Configuration and Power Interface Specification) and this function is under the presumption that the OS uses the space. Therefore, in order for BIOS (Basic Input/Output System) to use this function under the Pre-Boot environment, it is necessary to add a new function to the BIOS, which different from a BIOS standard specification.
Under the above circumstances, a new IO space resource assignment method for realizing a large-scaled IO system is demanded.
In conjunction with the above description, the following conventional examples are known.
Japanese Patent Publication (JP 2001-229117A; patent literature 1) discloses a computer and an extended unit control method. In the conventional technique, when connection between a PC and a docking station is detected and BIOS (SMI handler) is started, IO space assignment to a gate array connected to an ISA bus is disabled. Moreover, the I/O space is specified in an I/O window of a PCI-PCI bridge of the docking station. Further, the I/O space is assigned to a command block register of a PCI IDE (integrated Drive Electronics) controller. Then, processes such as initialization of a device mounted in the docking station, programming of a data transfer speed, release of a password, and so on are executed by transmitting an ATA command to the register, the IO space assignment is released, and completion of connection with the docking station is notified to an OS.
Japanese Patent Publication (JP 2008-191957A; patent Document 2) discloses a computer system and a file system automatic setting OS starting method. In this conventional technique, after initialization of the system is completed upon start of processing, whether or not an SCSI (Small Computer System Interface) card is mounted is determined based on a vendor ID and device ID of the SCSI card. If the SCSI card is mounted, whether or not there is setting of an Option ROM (extended ROM) as an effective start program for booting OS is determined. At time of OS booting for the first time, because there is no setting of the effective Option ROM, an automatic Option ROM setting validating process is started. In the automatic Option ROM setting validating process, a DISK connected to a SCSI card needs to be searched, and therefore, a first SCSI card slot is detected and an SCSI card slot number is detected and held. The Option ROM is temporarily validated for the detected slot, and an FS (file system) in the DISK under the SCSI card mounted in the detected SCSI card slot is read out. Then, whether the FS is an OS bootable file system is determined, and if the file system can be started by the OS, data indicating that the setting of the Option ROM is valid is stored into a RAM. Subsequently, whether the detected slot number is coincident with a final slot number is determined. If the slot number is not final, an SCSI slot number obtained by counting up the target slot number by “1” is held as a next target slot number. If the slot number is final, whether or not the setting of the Option ROM on the RAM has been changed is determined, and if it has been changed, the initialization of the apparatus is performed since the device requires reactivation.
Japanese Patent Publication (JP-A-Heisei 10-293684; Patent Document 3) discloses a computer system and a start-up control method. In this conventional example, a system BIOS of a BIOS-ROM system including a POST (Power-On-Self-Test) routine and a driver routine for extension is set to a protect mode, and a CPU address space after “100000h” which can be accessed only in the protect mode is assigned to this system BIOS, and an address space “F0000h to FFFFFh” which can be accessed in a real mode is assigned to the system BIOS including a BIOS driver group.
It should be noted that POST is a test to be automatically executed for each device such as a computer upon power supply, to check whether or not hardware has any default.